Fig 4. CD4 peptide inhibition of soluble ⍺₄β₇ binding to CD4 D1D2.

(A) SPR assay of soluble ⍺₄β₇ binding to a biosensor surface coated with sCD4 D1D2 in the absence (black) or presence of overlapping 15 aa peptides corresponding to residues encoded in CD4 D1 (p1-p21) and D2 (p22-p42). Binding of ⍺₄β₇ to the D1D2 coated surface is reported in response units (RU). p9 (green) and p42 (red) aa sequences are reported. (B) Ribbon diagram of D1 and D2 domains of CD4 (PDB: 1CDI), MAdCAM-1 (PDB: 1BQS) and VCAM-1 (PDB: 1IJ9). 1° binding sites are highlighted in red, and accessory binding sites are highlighted in green. Predicted metal ion coordination sites for each ligand are indicated (orange). (C) CD4 D1D2 residues with β-strand designations listed above. D1 residues are highlighted in orange and D2 residues in blue. p9 and p42 are highlighted in red and green.